Sheppard Software is always my go-to website because it really does have fabulous games. The students can interact with the Easter Egg Hunt or other spring activities listed on the site.
Primary Games also has a complete list of Easter and Spring games students could play during center or computer time. Some of them are purely just for fun so I would recommend showing them the games that focus more on a concept.
Other sites to check out....
A Kid's Heart
Hope you enjoy the activities...makes me excited for spring!